Tuesday, June 12, 2007

Balance and the Bandstand

Some thoughts on balance (that directly relate to our bandstand):

1. The bandstand is about the best anywhere, but it does have a few
quirks. If you look at the ceiling you can see that lines in the
plaster converge in the very center. These are decorative, but make it
easy to find the exact center of the stage. Directly under the center
of the ceiling there is a spot about a yard (or slightly more) in
diameter (circular) that is sort of dead. If you're sitting in that
spot your sound won't project as well. It has to do with resonance,
standing waves, and distances. It affects lower notes more than higher
notes. In effect, the sound waves reflect off the back wall back into
this spot and cancel out the waves coming from this spot, if the note's
wavelength is close to a multiple of the distance to the back wall. If
we can avoid having anyone sit directly under this spot it might help,
but since there are a "range" of distances to various portions of the
wall, there are different notes affected at different spots. This is a
very subtle effect, but enough to make certain notes "drop out" of the
overall sound. So, if you find that one of your notes sounds very loud
at this spot, THAT is the note that you hear and the audience doesn't,
so "favor" that note even louder.

2. There is a corridor from that center spot back to the open door in
the back of the bandstand, about a yard wide. If you're sitting in that
corridor your sound won't project to the audience quite as well. The
"hole" in the back wall allows the sound to be reflected off the wall at
the back of the backstage area back through the door, so it is out of
phase with the sound reflected off the back wall of the stage, creating
a "cancellation" of sound waves. Therefore if you are in this "corridor"
or in the "dead spot" (at church, in the choir loft we call our dead
spot the black hole) you need to play at least one dynamic level louder
than if you weren't sitting there. So, just look at the ceiling and at
the door, find the "dead corridor" and adjust if you're in it. In this
situation, if a certain note seems to be coming from inside your head,
you are hearing it out of phase and need to emphasize it a bit so it
sounds right to the audience.

3. If you are sitting outside the roof cover, your sound doesn't
project. In fact, this effect extends about a foot inside that line, so
if you are there, increase your dynamic level by 1 level. Usually this
is the person in the outermost chair.

4. The bandstand has a resonance. Back when I was a student at UVA, if
I was late to marching band practice at Scott Stadium, I could tell I
was late because you could hear the drums... but they didn't sound like
drums... it was one pitch over and over, because the air column inside
the stadium had its own resonant note. It's just like the "boom-boom"
sound from cars with loud stereos passing by... just one note. That's
because the trunk or door of the car has a resonance that is heard
outside but not inside the car. This resonance of the bandstand is
around Eb or F just below the bass staff. Somehow it isn't noticeable
in the tuba sound, but seems to be so in tympani and bass drum. I have
been working on the bass drum tuning. When you don't dampen it, the
resonance of the bandstand doesn't seem to be "triggered" but when you
do dampen it, we get a loud resonant tone that you probably can't hear
from the back of the bandstand. I need to move the pitch of the bass
drum just a little to see if we can get rid of that resonance. (It is
more noticeable when the drum is upright.)

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